Multilayer Microlaminated Ceramic Thermal Barrier Coating

摘要

This report describes the Phase I effort to develop a new-approach for applying micro-laminated thermal barrier coatings on superalloys through a sol-gel process. This Phase I has demonstrated the following: (1) Cubic zirconia (yttria-stabilized-zirconia) can be coated through a sol-gel process onto bond coated superalloys. The films have very good adhesion and cohesion demonstrated by tape test. The films on the other side of the superalloy without bond coat peeled off very easily. (2) Zircon can be coated onto the yttria-stabilized-zirconia layer as a reinforcement layer. The glassy phase may help to relieve the stress during thermal cycling. (3) Cubic zirconia can be coated onto the zircon layer. The feasibility of applying multilayer thermal barrier coating with micro-laminated structure through a sol-gel approach has been clearly demonstrated. (4) The cubic zirconia films are stable at 1100 C, which is close to the service temperature of a turbine engine. The crystallization of the cubic zirconia can be achieved at 500 C. This new approach has better control of not only the process parameters but also the coating compositions and microstructures. Both thermal and mechanical characteristics of the coatings can be potentially optimized.